You Can't Use The old Apple Pencil on The New iPad Pros

Alongside the new iPad Pro 11 and iPad Pro 12.9
Apple also introduced a second generation Pencil. In case it wasn’t
clear, the new tablets are not compatible with the old stylus and the
new stylus isn’t compatible with the old tablets.
A big part of that is charging – the new Apple Pencil is charged
wirelessly from the new iPad Pros while the old one plugged into the
Lightning port (which, by the way, the new tablets do not have). The
second-gen Pencil also attaches to the tablet with magnets, which
triggers a pairing process.

There are other differences too. The new Pencil supports a double tap
gesture that is used in apps. For example, it can switch between
drawing and erasing. That solves one of the pain points of the original,
but it also makes upgrading more expensive.
Not only do you need a new stylus, but the second-generation Apple
Pencil is more expensive too. It costs $130/€135 compared to $100/€100
for the original.